Many communication devices are mobile and operate on battery power. Such communication devices generally include a radio receiver and/or radio transmitter for radio communication, a user interface for controlling the communication device, and a rechargeable battery for powering the communication device.
An example of such a communication device is a radiotelephone. A radiotelephone includes a receiver and transmitter and operates in a radiotelephone system. The radiotelephone system includes one or more base stations coupled to the public switched telephone network (PSTN) and configured for completing calls between the radiotelephone and the PSTN. The radiotelephone, or mobile station, is portable and therefore free to move about within a fixed geographic area served by the base station. To improve mobility and user convenience, many radiotelephones are powered by rechargeable batteries. Other examples of such communication devices are paging receivers and land mobile radios.
One design goal for communication devices including radiotelephones is minimization of power consumption from the battery. One reason for this goal is to permit the use of physically smaller, lighter batteries. Such smaller and lighter batteries permit the communication device itself to be physically smaller and lighter, and thereby more convenient for the user. A second reason for minimizing power consumption in a communication device is to extend the operating time of the communication device, which also enhances convenience for the user.
Displays in communication devices are one source of substantial power consumption. Such displays include multi-segment light emitting diode (LED) displays and liquid crystal (LCD) displays. LCD and other displays often include backlighting using one or more LEDs to improve night time visibility of the display. In addition, the display may include individual elements such as LEDs which are selectively energized to provide a user indication. Still further, many communication devices having keypads provide one or more LEDs for backlighting the keypad for visibility in the dark.
One known method of reducing power consumption in a communication device is blanking the display a predetermined time after operation of the keypad. The display is blanked by removing power from portions of the display. Such portions include specific LED segments or LEDs used for backlighting a LCD display. Only one or a few isolated illuminated elements, such as LED indicators, remain energized to provide a visual indication that the communication device is active. By blanking the display, power consumption can be substantially reduced.
The rationale for blanking the display is that there are times when a user no longer needs to see the display. For example, once a user has initiated a telephone call, the user no longer needs to see the display. Also, when the user is not actively using the telephone and the user is awaiting an incoming call, the user does not need to see the display. The display is necessary when entering numbers using the keypad, for verifying accurate entry. The display is also necessary when operating other features of the user interface of the radiotelephone, such as recalling telephone numbers stored in the radiotelephone's memory. Once the call is connected and the user holds the radiotelephone against the user's head during the conversation, the display is not needed by the user and blanking is appropriate. The radiotelephone blanks the display after a preset time delay (such as 8 seconds) following the last keypress or following the opening of a keypad cover. This rationale applies to other types of communication devices as well.
In some instances, blanking can hinder user convenience. This can occur if the user is still holding the communication device in his hand and still wants to see the information on the display. Blanking at such a time is inconvenient for the user. According to current designs, in order to get the information on the display to reappear, the user must press a key on the keypad or close and open the keypad cover. Either action may produce undesired responses, such as changing the state of the communication device or ending an active call. There are other instances when display blanking can hinder user convenience. One of these is while trying to operate the communication device while driving, at times when the user's constant concentration on driving is required for more than 8 seconds. Another example is when using the communication device in the dark, when having keypad backlighting turned off makes it difficult to find keys including a key which will illuminate the display.
Accordingly, there is a need in the art for a method and apparatus for controlling the blanking in a communication device.